[time-nuts] sub-minute time-precision in court-case

Jim Lux jimlux at earthlink.net
Tue Sep 3 19:59:34 EDT 2013


On 9/3/13 11:21 AM, Poul-Henning Kamp wrote:
> In message <5225F8AF.60807 at earthlink.net>, Jim Lux writes:
>
>> In this case, all the messages were presumably handled by the same
>> carrier, so the issue of skew in timestamps is negligible;
>
> Anything but.
>
> The text-messages are likely stamped by the SS7-message-gateway
> and the 911 call by the countys 911 equipment.
>

I was assuming (with no real basis, I realize) that the 911 call time 
came from the cell equipment, rather than the Public Safety Answering 
Point log.  The PSAP log would have no particular reason to be synced to 
the carrier equipment. It could well be "what time was on the watch of 
the guy starting the equipment", although these days, one would *think* 
that they use something like NTP to set the system time.

However, given my frustrated experience trying to get folks doing 
testbeds and ground support equipment here at JPL to *please* 
synchronize your computers meaningfully so we can merge logs, I wouldn't 
count on it.  Or maybe they sync once every 24 hours.




> And yes, there can be quite a delay from you press "send" until
> the SS7-message-gateway sees the text-message.
>



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